Question

(Had it not been for )his teacher,Li Ming wouldn't have passed the English exam so easily.

括号处何解？为何不能填If it hadn't been?

Answer 1

Had it not been for 是 if it hadn't been for的省略形式
是虚拟语气的一种特殊用法
在if从句中，如果含有“were，should，had’’时，可省去if而将“were，should，had’’置于句首，构成倒装句。例如：
　　Were l in your position，1 would go．如果我处在你的位子上，我就走了。
　　Had you arrived five minutes earlier，you could have seen them off．如果你早到五分钟，

Answer 2

这是虚拟语气的倒装，
1当与过去相反时 去掉if 把had前置，Had you come to the party,you would have met ZhouBiChang
2当与现在相反时 去掉if 把were前置：Were I you ,I would go back
3当与将来相反时 去掉if 把should前置Should it rain ， the crop should be saved

Answer 3

可以填 If it hadn't been啊，这是对过去的虚拟，你写的句中省略了if